Sunday, January 20, 2013

1/20 - 2:45pm - Bitter Cold Air is Arriving Soon!

Temperatures in the 30's were common last night in West Tennessee and North Mississippi but temperatures are poised to drop much further than that tonight. A dry and relatively marginal cold front is moving through West Tennessee right now and that cold front is the first of two cold shots for the region. This will put lows down into the mid 20's in West Tennessee and lower to mid 30's in North Mississippi as cold air pours in behind the front. This cold air won't allow temperatures to rise much during the day tomorrow either, with highs in the upper 30's closer to Jackson, TN and closer to 50 down toward the Golden Triangle in Mississippi.

During the day tomorrow the second of two shots of cold air will pour in as another cold front passes by. This one will bring the ├╝ber cold weather that we'll see on Monday night and Tuesday morning. The winds behind this front will be out of the north, meaning the source region (AKA where the air is coming from) for the cold air we'll see during this time will be in the Upper Midwest where they'll be below zero. While that kind of cold isn't expected, mid to upper teens will be common in West Tennessee with readings closer to 20 or 25 degrees down toward North Mississippi. A low of 16 or 17 degrees in Jackson, TN on Tuesday morning looks pretty reasonable given the intensity of the cold air spilling down. While our neighbors to the north may scoff at this being branded as "bitterly cold" in the South, this is still some incredibly cold air. Pets will certainly need to be inside during this time and people need to be bundled up as much as possible. Limit your time outside on Tuesday morning, if possible, and be sure to cover any exposed skin if you do have to be out. Temperatures during the day on Tuesday will warm to a more reasonable lower 30's in West Tennessee and lower 40's in North Mississippi.

Temperatures will moderate during the week thanks to the return of wind flow from the south. This return flow means more moisture in the air across the region. You might guess that this warmer air and more moisture will eventually lead to rain chances... and you'd be right! A low pressure system and associated upper-level shortwave disturbance will track through near the end of the week, bringing rain chances. There's some disagreement between various models over whether this will start on Thursday or Friday. The GFS model's timeline on this is posted below. My guess at this point is that the timeline you see below will be delayed by about 12 hours, so expect rain chances to creep into the region ahead of this low on Thursday afternoon and continue through the night into Friday.

It's not out of the realm of possibility that a little bit of wintry precipitation may fall on the backside of this system on Friday. If cold air flows in behind a cold front associated with this system fast enough then some of the last few rain showers could mix with or change over to a brief period of snow. The GFS identifies Kentuckiana as being the prime target for this but we all know that model has been trending too warm lately in all the winter weather events we've dealt with. So in my mind, West Tennessee is in a potential area for this mix or snow switchover to occur. We're too early for specifics on this so the forecast will have to be fine-tuned during the week. Stay warm!

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